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UNITED STATES PATENT OFrIoE.

sconce n nowsnu, or NOR-TH ADAMS, MASSACHUSETTS.

.M'PROVEMENT IN BLAST lNG-POWDER Specification forming part of Letters Patent No. 150,428, dated May 5, 1874; application filed March 19, 1873.

To all whom titan/4 concern:

Be it knownthat I, GEORGE M. MowBuAv, of North Adams, in the county of Berkshire and State of ltlassachusctts, have invented an Improved Mica Blasting-Powder, of which the following is a specification:

The nature of my invention consists in forming an explosive blasting powder by mixing nitro -glyccrine with finelydivided mica or mnscovy tale in the form of scales, varying the relative proportions, so as to adapt the mixture, when used for blasting purposes, to transportation in any climate or season, and so as ,to modify the force of explosion when applied to artillery, shells, fixed ammunition,v sporting-guns, &c. The distinguishing feature of this compound from other mixtures of nitro-glycerine with inert matter consists in its elasticity or resilient properties, for on rammin g a ch argc of it into a cartridge, on withdrawin g the rannner, there is an immediate increase of bulk, the mixture being-quite elastic. This remarkable elastic property renders it not only safe to transport, but suitable forartillery, shells, fixed ammunition, small arms, &c. Further, owing to the extreme tenuity or thinness of mica scales, notwithstanding its heavy specific gravity (2.900) or density, a given bulk or weight presents an enormous surface; thus I have found twenty-five grams, or three hundred and eighty-six grains, well shaken down, of such scales will oceupya space of ten cubic inches, which would contain of water two thousand five hundred and thirty-two grains, (25318,) being less than one-sixth as heavy as water in the.form of scales finely divided, while in block masses it is nearly three times as heavy as water, (2.900.) Now, if we incorporate with these ti ree hundred and eighty-six grains of finely-divided mica, say, t eble their weight of nitro-glycerine, and then introduce the mixture into a glass graduated tube by ramming or pressure with the hand, it will be found to occupy six cubic inches and still retain much of the elastic property I have referred to. Calculation will show that in such a rammed tube there must exist two cubic inches and two-thirds of a cubic inch of interspace, besides the nitro-glycerine and finely-divided mica, occupied by atmospheric air, which explains the elasticity referred to.

The dan er arisin durin trans ortation of I liquid nitro-glycerinc is chiefly from concussion or leakage. It will, therefore, be obvious that this mixture, being elastic, protects the nitro'glycerine from the vibrations of concussion; meanwhile the adhesion or capillary at.- traction of the nitro-glycerine to the immense superficial area of the thin scales of mica also prevents leakage. bustion of dynamite or giant-powi'ler with the above mica blasting-powder, a remarkable difference will be observed. on applying a lighted match successively to each of them in the open air. While the mica compound gives a vivid voluminous flame, quadruple in volume thatyielded by dynamite or gian t-powder, and the particles of mica are carried up three feet into the air by the rapidmotion of heated gases, the flame of giant-powder and dynamite under the same conditions of temperature and quantity, is limited to one-fourth of the micamixture flame, and the residuarymattcr is not carried up by the heated gases. \Vhile neither giant-powder nor dynamite can be compared with the mica mixture in developing blasting force, this latter compares very favorably with liquid nitro-glyeerine in its pure state, and in the proportions stated above (three of nitroglycerine to one of mica scales) continuous experiments have convinced me that it fully develops the entire blasting effect of the nitroglycerine it contains, and does not, as is the well known fact with dynamite, dualin, and giant-powder, lose half its power as a blasting agentby mixture with the inert matter associated with it.

To enable any one skilled in the art to prepare the mica blasting-powder, the blocks of mica should be split into slabs of halfineh thickness and then offered to the teeth of a rotating rasp in rapid motion, being held pcrpen dicular to the edges of the plates of mica, and not sidewisc. Such small pieces as cannot be heldedgewise to the rasp may be divided up by subjecting thein to the action of edge-ruin 1101's. large meshes, say onc-quarter to thrce eighths of an inch. The mica is warmed to 80, and raked level in a tank, and nitro glycerine warmed to 80 Fahrenhcitis then poured over the finelydivided mica from the rose of a- On comparing the com- It is then sifted through a sieve with 1 watering-pot, stirring the mil {tare enrefully. The proportions of eachwilfdepend on the purpose to which it is to be applied. Where the greatest .possible fii plosive or blasting force is required, onepart of finely'divided rniga; to three parts of nitrogljeerine may be one part of nitroglycerine; for charging shells, and for the exploding charge of rockets, equal parts of mice and nitro-g'lyeerine; for small-arms, fixed mnmunition, &c.; to three or folu parts of mice two parts ofnitro-glyeerlne.

Experience and further experiments will develop the proportions for the varied proje'e tiles of modern warfare.

Having thus described my invent-ion, I claim- A combination of nitro-glycerine with finelyfining my invention to any specific proper tions-of the materials, as described. V GEORGE M. MOWBB'AY. Witnesses:

W. H, GnIswoLn, WM. K. BAR-LOW. 

